Migratory behaviour of eastern whip-poor-wills (Antrostomus vociferus): quantifying return rates and the effects of artificial light on flight paths
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Date
2023-08-19
Authors
Thompson, Stephanie
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Abstract
Migration poses significant challenges for organisms, especially those traveling long distances. It is hypothesized that despite these challenges, migration evolved as a method of resource maximization and competition reduction. Along with morphological adaptations, species often develop life history traits in complement with their migratory habits. Urbanization and artificial light have further complicated migration patterns for many species. This thesis was aimed at addressing gaps in our understanding of the life history of the Eastern Whip-poor-will (Antrostomus vociferus) in relation to their migratory behaviour and to determine the impact of artificial light on their migratory routes. I captured whip-poor-wills at their breeding locations in southern Manitoba and north-western Ontario and used direct-tracking technologies (archival GPS units; radio telemetry tags) to collect data on timing, routes, and return rates. I used the resulting migration tracks and Bayesian generalized linear models to test for an effect of artificial light levels on route tortuosity along fall migratory pathways. I found that whip-poor-wills took more indirect flight paths on nights when a direct path would result in exposure to more intense artificial light, suggesting they sacrifice efficiency for light avoidance. Next, I used 6 years of capture data, a displacement experiment, and automated radio-telemetry to quantify recapture rates and site-fidelity at breeding territories. I found evidence for high survival rates and site fidelity: annual recapture rates ranged from 50 – 80% and average recapture of birds on the same territory in subsequent years was 75%, 75% of birds returned after displacement, and 90% of radio-tagged birds survived to be detected by receiver towers along the spring migratory routes in the year following tagging birds. Since whip-poor-wills have a longer than average life span and lower annual clutch sizes for a small migratory land bird, my results showing high site fidelity and return rates align with predictions based upon these traits. My results demonstrating sensitivity to artificial light and high site fidelity could be incorporated into conservation and management planning for this threatened species.
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Keywords
Species-at-Risk, Migration Ecology, Avian Ecology, Nocturnal, Survival